U.S. patent number 11,298,446 [Application Number 14/577,236] was granted by the patent office on 2022-04-12 for systems and methods for calibrating pump stroke volumes during a blood separation procedure.
This patent grant is currently assigned to Fenwal, Inc.. The grantee listed for this patent is FENWAL, INC.. Invention is credited to Kathleen M. Higginson, Amit J. Patel, Samantha M. Planas.
United States Patent |
11,298,446 |
Planas , et al. |
April 12, 2022 |
Systems and methods for calibrating pump stroke volumes during a
blood separation procedure
Abstract
A method is provided for calibrating a pump during a blood
separation procedure that has at least a first and second state or
phase where fluid is flowed to or from a reservoir by action of the
pump. The state or phase of the procedure may be a priming state, a
draw state, a separation state and a return state, and the pump
calibration may be performed between consecutive performances of
the same procedure state. The calibration is based on a variance
between the volume of fluid predicted to be processed by the pump
for the given state of the procedure and the actual volume
processed based on the change of weight of the reservoir.
Recalibration of the pump, if necessary, is accomplished before the
performance of the second phase is commenced.
Inventors: |
Planas; Samantha M. (Wauconda,
IL), Patel; Amit J. (Algonquin, IL), Higginson; Kathleen
M. (Mount Prospect, IL) |
Applicant: |
Name |
City |
State |
Country |
Type |
FENWAL, INC. |
Lake Zurich |
IL |
US |
|
|
Assignee: |
Fenwal, Inc. (Lake Zurich,
IL)
|
Family
ID: |
55521317 |
Appl.
No.: |
14/577,236 |
Filed: |
December 19, 2014 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20160175509 A1 |
Jun 23, 2016 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61M
1/0209 (20130101); A61M 1/14 (20130101); A61M
1/3496 (20130101); A61M 1/265 (20140204); A61M
60/50 (20210101); A61M 1/267 (20140204); A61M
60/279 (20210101); A61M 60/113 (20210101); A61M
60/268 (20210101); A61M 2205/3334 (20130101); A61M
2205/702 (20130101) |
Current International
Class: |
A61M
1/26 (20060101); A61M 1/14 (20060101); A61M
1/34 (20060101); A61M 1/02 (20060101); A61M
60/50 (20210101); A61M 60/113 (20210101); A61M
60/268 (20210101); A61M 60/279 (20210101) |
References Cited
[Referenced By]
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Other References
European Search Report, counterpart EP Appl. No. 15200418 dated May
12, 2016. cited by applicant .
China National Intellectual Property Administration, Search Report
for counterpart application No. 201510864011.9, dated Mar. 25, 2019
(2 pages). cited by applicant.
|
Primary Examiner: Keyworth; Peter
Attorney, Agent or Firm: Cook Alex Ltd.
Claims
The invention claimed is:
1. A method for adjusting a pump flow rate during a blood
separation procedure having an initial performance of a first state
and a second performance of the first state where fluid is flowed
to or from a reservoir by the pump, the pump flow rate being
adjusted between the initial and second performances of the first
state, the method comprising: a) establishing a minimum volume of
fluid to be pumped during the initial performance of the first
state of the procedure in an amount to account for permissible
tolerances; b) providing a predetermined value for a flow rate of
fluid to or from the reservoir for the initial performance of the
first state of the procedure; c) weighing the reservoir at the
beginning of the initial performance of the first state of the
procedure; d) operating the pump to flow fluid to or from the
reservoir to perform the initial performance of the first state of
the procedure; e) weighing the reservoir at the end of the initial
performance of the first state of the procedure; comparing the
weight of the reservoir at the beginning of the initial performance
of the first state of the procedure to the weight of the reservoir
at the end of the initial performance of the first state of the
procedure to determine an actual volume of fluid pumped during the
initial performance of the first state of the procedure and to
determine an actual flow rate of fluid to or from the reservoir; g)
comparing the minimum volume of fluid to be pumped during the
initial performance of the first state of the procedure to the
actual volume of fluid pumped during the first state of the
procedure; h) if the actual volume of fluid pumped during the
initial performance of the first state of the procedure exceeds the
minimum volume of fluid to be pumped, then determining a variance
between the actual flow rate and the predetermined value for the
flow rate; i) calculating a pump volume for the initial performance
of the first state of the procedure; j) adjusting the predetermined
value for the flow rate for the second performance of the first
state of the procedure based on the variance, wherein a maximum
permissible adjustment of the predetermined value for the flow rate
from the initial performance of the first state to the second
performance of the first state is limited to a predetermined amount
that is less than the variance between the predetermined value for
the flow rate and the actual flow rate; and k) operating the pump
at the predetermined value for the flow rate for the second
performance of the first state of the procedure to flow fluid to or
from the reservoir to perform the second performance of the first
state of the procedure.
2. The method of claim 1 wherein the predetermined value for the
flow rate for the initial performance of the first state of the
procedure is obtained based on a nominal pump stroke volume and an
anticipated number of pump strokes to be performed by the pump.
3. The method of claim 1 wherein the first predetermined amount is
the calculated pump volume for the first state of the procedure is
from 10 mL to 1000 mL.
4. The method of claim 1 wherein the second predetermined amount is
from 1% to 50%.
5. The method of claim 1 wherein the second predetermined amount is
from 1 mL/min to 50 mL/min.
6. The method of claim 1 wherein the pump is a blood pump and the
first state of the procedure is a draw state.
7. The method of claim 1 wherein the pump is a blood pump and the
first state of the procedure is a return state.
8. The method of claim 1 wherein the pump is a cell pump and the
first state is a separation state.
9. The method of claim 1 wherein the pump is an AC pump and the
first state of the procedure is a prime state.
10. The method of claim 1 wherein the pump is an AC pump and the
first state of the procedure is a draw state.
11. The method of claim 1 in which the pump is a cell pump and the
fluid in the reservoir is a return fluid that has a target
hematocrit, the method further comprising reducing the target
hematocrit of the fluid in the reservoir if the pump recalibration
adjustment results in a slower pump speed.
12. The method of claim 1 in which the pump is a blood pump and the
fluid in the reservoir is a return fluid that has a target
hematocrit, the method further comprising reducing the target
hematocrit of the fluid in the reservoir if the pump recalibration
adjustment results in an increased pump speed.
13. In a blood separation procedure comprising one or more of a
priming state, a draw state, a separation state and a return state
and utilizing a system comprising a fluid circuit with at least one
reservoir and a pump for flowing fluid through the fluid circuit
during each state, a method for adjusting a pump flow rate for
consecutive performances of the same procedure state, comprising:
a) establishing a minimum volume of fluid to be pumped during the
initial performance of a selected first state of the procedure in
an amount to account for permissible tolerances; b) providing a
predetermined value for a flow rate of fluid to or from the
reservoir for the selected first state of the procedure; c)
weighing the reservoir at the beginning of the initial performance
of the selected first state of the procedure; d) operating the pump
to flow fluid to or from the reservoir for the initial performance
of the selected first state of the procedure; e) weighing the
reservoir at the end of the initial performance of the selected
first state of the procedure; f) comparing the weight of the
reservoir at the beginning of the initial performance of the
selected first state of the procedure to the weight of the
reservoir at the end of the initial performance of the selected
first state of the procedure to determine an actual volume of fluid
pumped during the initial performance of the selected first state
of the procedure and to determine an actual flow rate of fluid to
or from the reservoir; g) comparing the minimum volume of fluid to
be pumped during the initial performance of the selected first
state of the procedure to the actual volume of fluid pumped during
the initial performance of the selected first state of the
procedure; h) if the actual volume of fluid pumped during the
initial performance of the selected first state of the procedure
exceeds the minimum volume of fluid to be pumped, then determining
a variance between the actual flow rate and the predetermined value
for the flow rate; i) calculating a pump volume for the initial
performance of the selected first state of the procedure; j)
adjusting the predetermined value for the flow rate for a
subsequent performance of the selected first state of the procedure
based on the variance wherein a maximum permissible adjustment of
the predetermined value for the flow rate from the initial
performance of the selected first state to the subsequent
performance of the selected first state is limited to a
predetermined amount that is less than the variance between the
predetermined value for the flow rate and the actual flow rate; and
k) operating the pump at the predetermined value for the flow rate
for the subsequent performance of the selected first state of the
procedure to flow fluid to or from the reservoir for the subsequent
performance of the same state of the procedure.
14. The method of claim 13 wherein the predetermined value for the
flow rate for the initial performance of the selected first state
of the procedure is obtained based on a nominal pump stroke volume
and an anticipated number of pump strokes to be performed by the
pump.
15. The method of claim 13 wherein the predetermined amount is from
10 mL to 1000 mL.
16. The method of claim 13 wherein the second predetermined amount
is from 1% to 50%.
17. The method of claim 13 wherein the second predetermined amount
is from 1 mL/min to 50 mL/min.
18. The method of claim 13 wherein the pump is a blood pump and the
selected first state of the procedure is a draw state.
19. The method of claim 13 wherein the pump is a blood pump and the
selected first state of the procedure is a return state.
20. The method of claim 13 wherein the pump is a cell pump and the
selected first state of the procedure is a separation state.
21. The method of claim 13 in which the pump is a cell pump and the
fluid in the reservoir is a return fluid that has a target
hematocrit, the method further comprising reducing the target
hematocrit of the fluid in the reservoir if the pump recalibration
adjustment results in a slower pump speed.
22. The method of claim 13 in which the pump is a blood pump and
the fluid in the reservoir is a return fluid that has a target
hematocrit, the method further comprising reducing the target
hematocrit of the fluid in the reservoir if the pump recalibration
adjustment results in an increased pump speed.
Description
BACKGROUND
Field of the Disclosure
The invention relates to fluid separation systems and methods. More
particularly, the invention relates to systems employing spinning
membranes for fluid separation and methods for operating such
systems.
Description of Related Art
Various blood processing systems now make it possible to collect
particular blood constituents, instead of whole blood, from a blood
source such as, but not limited to, a container of previously
collected blood or other living or non-living source. Typically, in
such systems, whole blood is drawn from a blood source, a
particular blood component or constituent is separated, removed,
and collected, and the remaining blood constituents are returned to
the blood source. Removing only particular constituents is
advantageous when the blood source is a human donor, because
potentially less time is needed for the donor's body to return to
pre-donation levels, and donations can be made at more frequent
intervals than when whole blood is collected. This increases the
overall supply of blood constituents, such as plasma and platelets,
made available for transfer and/or therapeutic treatment.
Whole blood is typically separated into its constituents (e.g., red
cells, platelets, and plasma) through centrifugation, such as in
the AMICUS.RTM. separator from Fenwal, Inc. of Lake Zurich, Ill.,
or other centrifugal separation devices, or a spinning
membrane-type separator, such as the AUTOPHERESIS-C.RTM. and
AURORA.RTM. devices from Fenwal, Inc. Such separation devices
typically comprise a fluid circuit having a separation chamber,
sources or containers of various solutions, and collection
containers that are interconnected by tubing and which is mounted
onto a durable hardware component that includes pumps, clamps, and
sensors that are automatically operated by a programmable
controller to perform the desired blood separation procedure.
Operation of the system to perform the desired procedure requires
control of the fluid flow rates and volumes of fluid circulated
through the various components of the fluid circuit. Fluid flow
through the fluid circuit is caused by operation of the pumps
acting on the tubing segments associated therewith. Flow rates
through the tubings caused by the pumps may vary from procedure to
procedure, and even during the course of a single procedure, due to
factors such as variations in the tubing comprising the fluid
circuit, changes in inlet pressure, variations in how the fluid
circuit is mounted to the durable hardware component, variations in
the characteristics of the biological fluid being processed (such
as variations in hematocrit), etc. Given the potential for
variation in flow rates and volumes, it is necessary to monitor
and, if necessary, adjust the operation of the pumps to insure that
the separation procedure is safely and efficiently performed. By
way of the present disclosure, systems and methods for calibrating
pump stroke volumes during a blood separation procedure are
provided.
SUMMARY
There are several aspects of the present subject matter which may
be embodied separately or together in the devices and systems
described and claimed below. These aspects may be employed alone or
in combination with other aspects of the subject matter described
herein, and the description of these aspects together is not
intended to preclude the use of these aspects separately or the
claiming of such aspects separately or in different combinations as
set forth in the claims appended hereto.
In a first aspect, a method is provided for calibrating a pump
during a blood separation procedure that has at least a first and
second state or phase where fluid is flowed to or from a reservoir
by action of the pump. The state or phase of the procedure may be
one or more of a priming state, a draw state, a separation state
and a return state, and the pump calibration may be performed
between consecutive performances of the same procedure state.
The method includes the steps of: providing a predetermined value
for the flow rate of fluid to or from the reservoir for the first
state of the procedure; obtaining the weight of the reservoir at
the beginning of the first state of the procedure; operating the
pump to perform the first state of the procedure; obtaining the
weight of the reservoir at the end of the first state of the
procedure; comparing the weight of the reservoir at the beginning
of the first state of the procedure to the weight of the reservoir
at the end of the first state of the procedure to determine an
actual flow rate of fluid to or from the reservoir; determining the
variance between the actual flow rate and the predetermined value
for the flow rate; and adjusting the value for the predetermined
flow rate for the second state of the procedure based on the
variance. Preferably, the weight is converted to a volume by
knowledge of the density of the fluid being pumped, and then
determining the flow rate as a volume per unit time.
In another aspect of the method, the value for the predetermined
flow rate for the pump is obtained based on a nominal pump cycle or
stroke volume for the pump and an anticipated number of pump cycles
or strokes to be performed by the pump during the performance of
the first state.
In a further aspect, the predetermined value for the flow rate for
the second state of the procedure is adjusted if a calculated pump
volume for the first state of the procedure exceeds a predetermined
amount. In one example, the predetermined value for the flow rate
for the second state of the procedure is adjusted if the calculated
pump volume for the first state of the procedure is from 10 mL to
1000 mL, and more preferably from 50 mL to 600 mL.
In another aspect of the method, a limit is set for the amount by
which the predetermined flow rate will be adjusted for the second
state of the procedure if the variance between the predetermined
value for the flow rate and the actual flow rate is greater than or
equal to (.gtoreq.) a set percentage or volume, in which case the
predetermined value for the flow rate for the second state of the
procedure is adjusted by no more than the set percentage or volume.
The set percentage may be within a range, e.g., of from 1% to 50%,
and preferably of from 5% to 25%. Similarly, the set volume may be
in a range of from 1 mL/min to 50 mL/min, and preferably from 5
mL/min to 25 mL/min.
In a further aspect of the method, the pump may be a blood pump and
the state of the procedure may be a separation state or a return
state; the pump may be an anticoagulant or AC pump and the state of
the procedure may be a prime state or a draw state; or the pump may
be a concentrated cell pump and the state of the procedure may be a
separation state.
In a related aspect, a blood processing system for processing whole
blood or a whole blood component is provided in which the
processing system comprises at least one pump and a controller with
a user interface and has a fluid flow circuit with at least one
reservoir associated therewith, and the controller is configured to
perform the methods of any one, or combination of, the aspects
described above.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a front perspective view of an exemplary fluid separation
system suitable for performing the method of the present
disclosure;
FIG. 2 is a rear perspective view of the fluid separation system of
FIG. 1, with a rear door thereof in an open position;
FIG. 3 is a front perspective view of the fluid separation system
of FIG. 1, with a fluid flow circuit associated therewith;
FIG. 4 is a front perspective view of a fluid separation chamber of
the fluid flow circuit of FIG. 3, with a portion thereof broken
away for illustrative purposes;
FIG. 5 is a schematic view of the fluid flow circuit and fluid
separation system of FIG. 3, in a fluid draw mode; and
FIG. 6 is a schematic view of the fluid flow circuit and fluid
separation system of FIG. 3, in a fluid return mode.
FIG. 7 is a flow chart schematically illustrating the various steps
of the pump calibration method of the present disclosure.
DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS
The embodiments disclosed herein are for the purpose of providing
an exemplary description of the present subject matter. They are,
however, only exemplary, and the present subject matter may be
embodied in various forms. Therefore, specific details disclosed
herein are not to be interpreted as limiting the subject matter as
defined in the accompanying claims.
According to an aspect of the present disclosure, a durable or
reusable fluid separation system is used in combination with a
separate fluid flow circuit (which may be disposable) to separate a
fluid into two or more constituent parts. FIGS. 1 and 2 illustrate
an exemplary fluid separation system 10, while FIG. 3 illustrates
an exemplary fluid flow circuit 12 mounted onto the fluid
separation system 10, but it should be understood that the
illustrated fluid separation system 10 and fluid flow circuit 12
are merely exemplary of such systems and circuits and that
differently configured fluid separation systems and fluid flow
circuits may be provided without departing from the scope of the
present disclosure.
The system 10 of FIG. 1 is configured for processing whole blood,
but it may be used to process other biological fluids. The fluid
may come from any fluid source during a draw or collection phase of
the procedure (see, e.g., FIG. 5) and be returned to any recipient,
which may be the same as or different from the fluid source, during
a return or reinfusion stage (see, e.g., FIG. 6). In one
embodiment, the fluid source/recipient is a living donor or patient
(e.g., a human blood donor), while in other embodiments the fluid
source and/or fluid recipient may be a non-living source/recipient
(e.g., a blood bag or fluid container).
The illustrated system 10 includes a cabinet or housing 14, with
several components positioned outside of the cabinet 14 (e.g.,
associated with a front wall or surface or panel of the cabinet 14)
and additional components (including a programmable central
processing unit or controller 16) and interconnects positioned
inside of the cabinet 14, which may be accessed by opening a rear
door 18 of the system 10, as shown in FIG. 2. Among the system
components positioned on the outside of the cabinet 14, one or more
pumps or pump stations 20a-20c may be provided, with the pumps
20a-20c configured to accommodate tubing lines of the fluid flow
circuit 12.
One of the pumps 20a may be provided as a source/recipient access
pump, which may be associated with a source/recipient access line
22 of the fluid flow circuit 12 and operates to draw fluid from a
fluid source (FIG. 5) during the draw or collection phase, operates
in reverse to return fluid to a fluid recipient (FIG. 6) during the
reinfusion stage, and is stopped at the end of the reinfusion
phase. Pump 20a also primes the fluid flow circuit 12 and clears
air from the access line 22. Pump 20a may also be referred to
herein as a "blood pump," as it serves to pump whole blood from its
source (such as a donor or, in the case of previously collected
blood, a container or reservoir) to the separation module or
chamber 28, described below. Pump 20a is also used to return the
non-targeted blood components.
Another one of the pumps 20b may be provided as an anticoagulant
pump, which may be associated with an anticoagulant line 24 of the
fluid flow circuit 12 and operates to add anticoagulant from an
anticoagulant source or container 26 of the fluid flow circuit 12
(FIG. 5) to fluid drawn from the fluid source in the
source/recipient access line 22 before the fluid enters into a
fluid separation module or chamber 28 of the fluid flow circuit 12.
The anticoagulant container 26 is supported by a weigh scale hanger
29. Pump 20b does not, however, operate during the reinfusion phase
of the procedure. Pump 20b may also be referred to herein as an "AC
pump."
A third pump 20c may be provided as a return fluid pump, which may
be associated with a return fluid outlet line 30 and operates to
draw a return fluid (i.e., a fluid constituent to be returned to a
fluid recipient) from the fluid separation chamber 28 and direct it
into a return fluid reservoir 32 after the fluid has been separated
into a return fluid and a collection fluid in the fluid separation
chamber 28. The return fluid reservoir is supported by the weigh
scale hanger 33. The pump 20c may also be used to prime the fluid
flow circuit 12 and assist in clearing fluid from the fluid
separation module 28 at the end of the procedure. Pump 20c does
not, however, operate during the reinfusion phase of the procedure.
Pump 20c may also be referred to herein as a "cell pump," as it
serves to deliver cellular concentrate (i.e., concentrated red
blood cells) to the return fluid reservoir 32 in a plasmapheresis
procedure.
In the illustrated embodiment, the pumps 20a-20c are peristaltic
pumps, but it is within the scope of the present disclosure for
differently configured pumps, such as diaphragm or other pumps, to
be provided. Furthermore, additional or alternative pumps may be
provided without departing from the scope of the present
disclosure. For example, a pump may be associated with a collection
fluid outlet line 34 of the fluid flow circuit 12 to draw a
collection fluid from the fluid separation chamber 28 after the
fluid from the fluid source has been separated into a return fluid
and a collection fluid. Also, as will be described in greater
detail herein, the illustrated embodiment employs a single fluid
flow tubing or flow path for both drawing fluid from a source and
flowing or returning it to a recipient, which are carried out
intermittently. The system 10 could employ separate draw and return
flow paths or tubes without departing from the scope of the present
disclosure.
In addition to the pumps 20a-20c, the external components of the
system 10 may include one or more clamps or valves 36a-36d
associated with the tubing lines of the fluid flow circuit 12. The
clamps or valves 36a-36d may be variously configured and operate to
selectively allow and prevent fluid flow through the associated
tubing line. In the illustrated embodiment, one clamp or valve 36a
may be provided as a fluid source/recipient clamp, which may be
associated with a draw branch 22a of the source/recipient access
line 22 of the fluid flow circuit 12 to allow (FIG. 5) or prevent
(FIG. 6) the flow of fluid through the draw branch 22a of the
source/recipient access line 22. Another one of the clamps or
valves 36b may be provided as a reinfusion clamp or valve, which
may be associated with a reinfusion branch 22b of the
source/recipient access line 22 downstream of a return fluid
reservoir 32 of the fluid flow circuit 12 to allow (FIG. 6) or
prevent (FIG. 5) the flow of return fluid through the reinfusion
branch 22b. A third clamp or valve 36c may be provided as a
collection fluid clamp or valve, which may be associated with the
collection fluid outlet line 34 to allow (FIG. 5) or prevent (FIG.
6) the flow of collection fluid through the collection fluid outlet
line 34 and into a collection fluid container 38, which is
supported by the weigh scale hanger 39. A fourth clamp or valve 36d
may be provided as a replacement fluid clamp or valve, which may be
associated with a replacement fluid line 40 of the fluid flow
circuit 12 to allow or prevent the flow of a replacement fluid out
of a replacement fluid source 42 (e.g., a bag or container at least
partially filled with saline). Additional or alternative clamps or
valves may also be provided without departing from the scope of the
present disclosure.
The illustrated system 10 further includes one or more pressure
sensors 43a and 43b that may be associated with the fluid flow
circuit 12 to monitor the pressure within one or more of the tubing
lines of the fluid flow circuit 12 during operation of the pumps
20a-20c and clamps or valves 36a-36d. In one embodiment, one
pressure sensor 43a may be associated with a tubing line that draws
fluid from a fluid source and/or directs processed fluid to a fluid
recipient, while the other pressure sensor 43b may be associated
with a tubing line that directs fluid into or out of the fluid
separation chamber 28 to assess the pressure within the fluid
separation chamber 28, but the pressure sensors 43a and 43b may
also be associated with other tubing lines without departing from
the scope of the present disclosure. The pressure sensors 43a and
43b may send signals to the system controller 16 that are
indicative of the pressure within the tubing line or lines being
monitored by the pressure sensor 43a, 43b. If the controller 16
determines that an improper pressure is present within the fluid
flow circuit 12 (e.g., a high pressure due to an occlusion of one
of the tubing lines), then the controller 16 may instruct one or
more of the pumps 20a-20c and/or one or more of the clamps or
valves 36a-36d to act so as to alleviate the improper pressure
condition (e.g., by reversing the direction of operation of one of
the pumps 20a-20c and/or opening or closing one of the clamps or
valves 36a-36d). Additional or alternative pressure sensors may
also be provided without departing from the scope of the present
disclosure. In addition, the system 10 preferably includes an air
detector 41 associated with the donor line 22 to provide a signal
to the controller 16 when air is detected in the donor line.
The system 10 may also include a separation actuator 44 that
interacts with a portion of the fluid separation chamber 28 to
operate the fluid separation chamber 28. A chamber lock 46 may also
be provided to hold the fluid separation chamber 28 in place with
respect to the system cabinet 14 and in engagement with the
separation actuator 44. The configuration and operation of the
separation actuator 44 depends upon the configuration of the fluid
separation chamber 28. In the illustrated embodiment, the fluid
separation chamber 28 is provided as a spinning membrane-type
separator, such as a separator of the type described in greater
detail in U.S. Pat. Nos. 5,194,145 and 5,234,608 or in PCT Patent
Application Publication No. WO 2012/125457 A1, each of which is
incorporated herein by reference. If provided as a spinning
membrane-type separator, the fluid separation chamber 28 may
include a tubular housing 48 (FIG. 4), with a microporous membrane
50 positioned therein. An inlet 52 allows a fluid from a fluid
source to enter into the housing 48 (via the draw branch 22a of the
source/recipient access line 22), while a side outlet 54 allows
return fluid to exit the housing 48 (via the return fluid outlet
line 30) and a bottom outlet 56 allows collection fluid to exit the
housing 48 (via the collection fluid outlet line 34) after the
fluid from the fluid source has been separated into return fluid
and collection fluid.
In the illustrated embodiment, the separation actuator 44 is
provided as a driver that is magnetically coupled to a rotor 58 on
which the membrane 50 is mounted, with the separation actuator 44
causing the rotor 58 and membrane 50 to rotate about the central
axis of the housing 48. The rotating rotor 58 and membrane 50
create Taylor vortices within a gap 60 between the housing 48 and
the membrane 50, which tend to transport the return fluid away from
the membrane 50 to exit the fluid separation chamber 28 via the
side outlet 54, while the collection fluid passes through the
membrane 50 toward the central axis of the housing 48 to exit the
fluid separation chamber 28 via the bottom outlet 56. In one
embodiment, whole blood from a blood source is separated into
cellular blood components (return fluid) and substantially
cell-free plasma (collection fluid). It should be understood that
the present disclosure is not limited to a particular fluid
separation chamber and that the illustrated and described fluid
separation chamber 28 is merely exemplary. For example, in other
embodiments, a differently configured spinning membrane-type fluid
separation chamber may be employed (e.g., one in which the membrane
50 is mounted on an inside surface of the housing 48 or on both the
rotor 58 and an inside surface of the housing 48 and facing the gap
60) without departing from the scope of the present disclosure.
The membrane 50 of the fluid separation chamber 28 may be variously
configured without departing from the scope of the present
disclosure. When the system 10 is to be used to separate blood into
two or more constituents, at least a portion of the membrane 50
preferably has anti-thrombogenic characteristics to prevent or at
least decrease the incidence of reaction, such as protein or
platelet activation upon the blood being separated within the fluid
separation chamber 28. As used herein, the term "anti-thrombogenic"
is intended to refer to a substance or property characterized by an
enhanced resistance to the accumulation of blood components than
the materials typically employed in the manufacture of membranes of
spinning membrane-type fluid separation chambers (e.g., nylon
6-6).
Any suitable membrane material (or combination of materials) and
anti-thrombogenic material (or combination of materials) may be
used in manufacturing the membrane 50. In one embodiment, the
membrane 50 is formed of a polymeric material (e.g., nylon 6-6,
polyethersulfone, polysulfone, polycarbonate, polyvinylidene
fluoride, polyamide, or the like), with an anti-thrombogenic
material (e.g., polyethylene glycol or any one of the additives or
coatings provided by Interface Biologics, Inc. of Toronto, Canada,
or the like) incorporated or mixed or blended therein. In another
embodiment, the membrane 50 is fully formed from a polymeric
material (e.g., nylon, polyethersuflone, polysulfone,
polycarbonate, polyvinylidene fluoride, polyamide, or the like) and
then an anti-thrombogenic material (e.g., polyethylene glycol, any
one of the additives or coatings provided by Interface Biologics,
Inc. of Toronto, Canada, or the like) is applied to or coated onto
at least a portion of the formed membrane 50.
According to one method of using the fluid separation system 10 and
fluid flow circuit 12, a fluid is drawn from a fluid source into
the fluid separation chamber 28 during a draw or collection phase
or mode (FIG. 5), where the fluid is separated into return fluid
(e.g., concentrated cellular blood components) and collection fluid
(e.g., substantially cell-free plasma). The collection fluid is
retained by the system 10, while the return fluid is stored in the
reservoir 32 and then returned to the fluid source during a return
or reinfusion phase or mode (FIG. 6). In one embodiment, the
sequential performance of the draw and return phases (drawing from
the fluid source, separating the fluid from the fluid source into
return fluid and collection fluid, pumping the collection fluid to
the fluid source or a different recipient, and returning the return
fluid to the fluid source) are repeated until a target (e.g., a
particular amount of collection fluid) is achieved. All of the draw
phases and all of the return phases may be identical or may differ
from each other. For example, a final draw phase may draw less
fluid from the fluid source than the previous draw phases and a
final return phase may infuse a combination of return fluid and
replacement fluid to the fluid recipient, whereas the previous
return phases pump only return fluid to the fluid recipient.
In accordance with the disclosure, a method is provided for
calibrating a pump during a blood separation procedure that has at
least a first and second state or phase where fluid is flowed to or
from a reservoir by action of the pump. The state or phase of the
procedure may be a priming state, a draw state, a separation state
and a return state, and the pump calibration may be performed
between consecutive performances of the same procedure state. In
the context of the system 10 described above, the reservoir may be
any one or more of the AC container 26, return fluid reservoir 32,
collection container 38, and replacement fluid source 42, depending
on the phase of the procedure being performed. For example, if the
separation phase of the procedure is being performed, the
"reservoir" would include both the return fluid reservoir 32 and
the collection container 38, as both have fluid flowed thereto
during the separation phase by pumps 20a and 20c. Thus, the pump
may be any one or more of pumps 20a, 20b and 20c.
Turning to FIG. 7, the steps of the pump calibration method,
generally designated 100, are schematically illustrated. As
contemplated, the steps of the method are preferably automatically
implemented by the system controller 16, described above. The
method 100 has an initial step 102 of providing a predetermined
flow rate of fluid to or from the reservoir or "pump efficiency"
for the first state of the procedure. This predetermined flow rate
may be input to the controller by an operator or preprogrammed into
the controller. The initial predetermined flow rate is typically
determined empirically. For example, the initial predetermined flow
rate for the pump may obtained based on a nominal pump cycle or
stroke volume for the pump and an anticipated number of pump cycles
or strokes to be performed by the pump during the performance of
the first state of the procedure.
The weight of the reservoir at the beginning of the first state of
the procedure is obtained, as indicated by step 104. The weight of
the reservoir may be obtained, e.g., by a weigh scale that supports
or is otherwise associated with the reservoir, such as weigh scales
29 and 33 described above, and which transmits a signal indicative
of the weight to the system controller 16.
The pump is then operated to perform the first state of the
procedure, as indicated by step 106. At the end of the first state
of the procedure, the weight of the reservoir obtained and
transmitted to the system controller, as indicated by step 108, and
the weight of the reservoir at the beginning of the first state
procedure is compared by the system controller to the weight of the
reservoir at the end of the first state of the procedure to
determine an actual flow rate of fluid to or from the reservoir, as
indicated by step 110.
The system controller then determines the variance between the
actual flow rate and the predetermined flow rate, as indicated by
step 112, and the predetermined flow rate or "pump efficiency" to
be used when performing the second state of the procedure is
adjusted by the system controller based on the variance, as
indicated by step 114. It may be that the pump is used for a
different state or phase of the separation procedure before it is
re-used for performing the second state of the procedure. Thus
weight measurements, flow rates, and pump efficiencies may be
stored by the system controller for a period of time before the
recalibration is actually performed.
In order to ensure that pump recalibration has a meaningful basis,
the amount of fluid pumped during the phase should be sufficiently
great so that permissible tolerances in, e.g., measurement of the
reservoir weight, and noise inherent in the system do not dominate
the determination of the variance between the calculated and
measured flow rates. Thus, in keeping with a further aspect of the
method, the predetermined flow rate for the second state of the
procedure is adjusted if the calculated pump volume for the first
state of the procedure exceeds a predetermined amount. In one
non-limiting example, the predetermined flow rate for the second
state of the procedure is adjusted if the calculated pump volume
for the first state of the procedure is from 10 mL to 1000 mL, and
more preferably from 50 mL to 600 mL.
Similarly, it may also be desirable to limit the magnitude of the
maximum permissible pump recalibration adjustment from the first
state to the second state. For example, even if the variance
between the predetermined flow rate and the actual flow rate is
greater than or equal to (.gtoreq.) a predetermined percentage, the
predetermined flow rate for the second state of the procedure is
adjusted by no more than the predetermined percentage. The
predetermined percentage may be in a range of, e.g., from 1% to
50%, and preferably from 5% to 25%. In a non-limiting example, the
predetermined percentage may be 10%, in which case if the variance
between the predetermined flow rate and the actual flow rate
exceeds 10%, the predetermined flow rate for the second state of
the procedure will be adjusted by no more than 10%. Alternatively,
the maximum permissible pump recalibration adjustment may be a
specified flow rate, within a range of, e.g., from 1 mL/min to 50
mL/min, and preferably form 5 mL/min to 25 mL/min. In a
non-limiting example, predetermined flow rate may be 10 mL/min, in
which case if the variance between the predetermined flow rate and
the actual flow rate exceeds 10 mL/min, the predetermined flow rate
for the second state of the procedure will be adjusted by no more
than 10 mL/min.
There may be instances where it would be appropriate for the system
to automatically adjust, or prompt the system operator to adjust,
other parameters for the separation procedure in response to
automatic recalibration of the pumps. For example, if automatic
recalibration would result in a slower cell pump speed or an
increased blood pump speed during the draw state, it may be
desirable to adjust the separation parameters by, e.g., reducing
the target hematocrit of the return fluid to reduce the likelihood
of hemolysis. Alternatively, the controller could by default always
reduce the target hematocrit of the return fluid at the beginning
of each draw cycle.
It will be understood that the embodiments and examples described
above are illustrative of some of the applications of the
principles of the present subject matter. Numerous modifications
may be made by those skilled in the art without departing from the
spirit and scope of the claimed subject matter, including those
combinations of features that are individually disclosed or claimed
herein. For these reasons, the scope hereof is not limited to the
above description but is as set forth in the following claims, and
it is understood that claims may be directed to the features
hereof, including as combinations of features that are individually
disclosed or claimed herein.
Without limiting any of the foregoing, the subject matter herein
may be found in one or more methods or apparatus. For example, in a
first aspect, a method is provided for calibrating a pump during a
blood separation procedure that has at least a first and second
state or phase where fluid is flowed to or from a reservoir by
action of the pump. The state or phase of the procedure may be a
priming state, a draw state, a separation state and a return state,
and the pump calibration may be performed between consecutive
performances of the same procedure state. The method includes the
steps of: providing a predetermined value for the flow rate of
fluid to or from the reservoir for the first state of the
procedure; obtaining the weight of the reservoir at the beginning
of the first state of the procedure; operating the pump to perform
the first state of the procedure; obtaining the weight of the
reservoir at the end of the first state of the procedure; comparing
the weight of the reservoir at the beginning of the first state
procedure to the weight of the reservoir at the end of the first
state of the procedure to determine an actual flow rate of fluid to
or from the reservoir; determining the variance between the actual
flow rate and the predetermined value for the flow rate; and
adjusting the value for the predetermined flow rate for the second
state of the procedure based on the variance.
In another aspect of the method, the value for the predetermined
flow rate for the pump is obtained based on a nominal pump cycle or
stroke volume for the pump and an anticipated number of pump cycles
or strokes to be performed by the pump during the performance of
the first state.
In a further aspect, the predetermined value for the flow rate for
the second state of the procedure is adjusted if a calculated pump
volume for the first state of the procedure exceeds a predetermined
amount. In one example, the predetermined value for the flow rate
for the second state of the procedure is adjusted if the calculated
pump volume for the first state of the procedure is the calculated
pump volume for the first state of the procedure is from 10 mL to
1000 mL, and more preferably from 50 mL to 600 mL.
In another aspect of the method, a maximum permissible pump
recalibration adjustment from the first state to the second state
is limited to a predetermined amount that is less than the variance
between the predetermined flow rate and the actual flow rate, the
predetermined amount being from 1% to 50%, and preferably from 5%
to 25%. Alternatively, a maximum permissible pump recalibration
adjustment from the first state to the second state is limited to a
predetermined amount that is less than the variance between the
predetermined flow rate and the actual flow rate, the predetermined
amount being from 1 mL/min to 50 mL/min, and preferably from 5
mL/min to 25 mL/min.
In a further aspect of the method, the pump may be a blood pump and
the state of the procedure may be a draw state or a return state;
the pump may be an anticoagulant or AC pump and the state of the
procedure may be a prime state or a draw state; or the pump may be
a return or cell pump and the state of the procedure may be a
separation state.
In a related aspect, a blood processing system for processing whole
blood or a whole blood component is provided in which the
processing system comprises at least one pump and a controller with
a user interface and has a fluid flow circuit with at least one
reservoir associated therewith, and the controller is configured to
perform the methods of any one, or combination of, the aspects
described above.
It will be understood that the embodiments described above are
illustrative of some of the applications of the principles of the
present subject matter. Numerous modifications may be made by those
skilled in the art without departing from the spirit and scope of
the claimed subject matter, including those combinations of
features that are individually disclosed or claimed herein. For
these reasons, the scope hereof is not limited to the above
description, but is set forth in the following claims.
* * * * *